Don't just practice running off the bike a lot, practice running at a sensible pace off the bike (ie SLOWER than you feel like you need/want to). After having the ground zoom by under your gaze for many hours at a relatively high rate of speed, when you start running, tendency is to feel like you are running horribly slow, when in fact you are not. So you press, and end up running too fast. Even figuring that out at the first mile marker, if you are using your watch, can be too late. Use watch and landmarks or GPS or whatever to make your t-runs realistic. Goal is to get comfortable, not to win the t-run. Just because you can come off an 80-100 mile ride and kill yourself to run a couple of miles at X:00 doesn't mean you should. Run slow, get into rhythm, and practice exactly what you'd ideally do in the race (which is not only not start too fast, but begin eating/drinking as soon as you can) - even though you're only going for 20-40 minutes, pretend you are going to be going for hours. Drink at each mile if that's the plan in the race (take a bottle to facilitate that). Have that first gel and maybe the second one. Bonus benefit, your recovery will be better than if you battled through the t-run with no intake just because you could get away with it and collapsed on the couch.